The specialty field of laboratory animal medicine and care covers a diverse array of responsibilities. Comparative Medicine Branch (CMB) staff may encounter unusual clinical cases and emerging murine infectious diseases during their normal work duties that are conducive to study. The construction and management of facilities for human emerging diseases and potential bioterrorism agent research also results in unique experiences. Publication of these findings and experiences contributes to advancing the laboratory animal field's body of knowledge, which may consequently result in: decreased confounding variables within animal studies; information about clinical changes observed in animals i.e. are the changes due to research use or are they a spontaneous problem?; and decreased cost for other entities that decide to build facilities to study emerging diseases and bioterrorism agents. Adventitious murine norovirus (MNV) and Spironucleus muris infections identified in research mouse colonies were studied. MNV is an emerging viral contaminant of mice with the potential to confound immunology research. S. muris is a protozoan rarely found in rodent colonies; it is also reported to confound immunology research.